Environmental Science

Chapter 13:

Energy

Key Concepts

Energy use in the U.S. and around world

Tradeoffs of different fossil fuels

Tradeoffs of nuclear energy

Improving energy efficiency

Energy saving options for cars

Fig. 13-3, p. 287

Commercial Energy for the World and US

Fig. 13-4, p. 288Year

21002025195018751800

0

20

40

60

80

100

Co

ntr

ibu

tio

n t

o t

ota

l en

erg

yco

nsu

mp

tio

n (

per

cen

t)

Wood

Coal

Oil

Nuclear

HydrogenSolar

Natural gas

Commercial Energy Use in US Since 1800

Fig. 13-5a, p. 289

Space Heating

Passive solar

Natural gas

Oil

Active solar

Coal gasification

Electric resistance heating(coal-fired plant)Electric resistance heating (natural-gas-fired plant)

Electric resistance heating(nuclear plant)

0.3

0.4

0.4

1.5

1.9

4.5

4.9

5.8

Net Energy Ratios

Fig. 13-7, p. 292

Major Oil, Natural Gas, and Coal Deposits in North America

Ample supply for 42-93 years

Low cost (with huge subsidies)

High net energy yield

Easily transported withinand between countries

Low land use

Technology is welldeveloped

Efficient distribution system

Advantages

Trade-Offs

Conventional Oil

Disadvantages

Need to find substitute within 50 years

Artifically low price encourages waste and discourages search for alternative

Air pollution when burned

Releases CO2 when burned

Moderate water pollution

Fig. 13-9, p. 293

Tradeoffs of Conventional Oil Use

Carbon Dioxide Emissions Per Unit Energy of Different Fuels

Nuclear power

Natural gas

Oil

Coal

Synthetic oil and gasproduced from coal

Coal-firedelectricity

17%

58%

86%

100%

150%

286%

Fig. 13-10, p. 294

Oil sand92%

Good fuel for fuel cells and gas turbines

Low land use

Easily transported by pipeline

Moderate environmental impact

Lower CO2 emissions thanother fossil fuels

Less air pollution than other fossil fuels

Low cost (with huge subsidies)

High net energy yield

Ample supplies (125 years)

Sometimes burned off andwasted at wells because of lowprice

Shipped across ocean as highlyexplosive LNG

Methane (a greenhouse gas) can leak from pipelines

Releases CO2 when burned

Nonrenewable resource

Difficult to transfer from one countryto another

Requires pipelines

Advantages

Trade-Offs

Conventional Natural Gas

Disadvantages

Fig. 13-13, p. 296

Tradeoffs of Natural Gas

Fig. 13-14, p. 296

Increasing moisture content

Increasing heat and carbon content

Peat(not a coal)

Lignite(brown coal)

Bituminous Coal(soft coal)

Anthracite(hard coal)

Heat

Pressure Pressure Pressure

Heat Heat

Partially decayedplant matter in swampsand bogs; low heatcontent

Low heat content;low sulfur content;limited supplies inmost areas

Extensively usedas a fuel becauseof its high heat contentand large supplies;normally has ahigh sulfur content

Highly desirable fuelbecause of its highheat content andlow sulfur content;supplies are limitedin most areas

Coal

Low cost (with huge subsidies)

High net energy yield

Ample supplies(225–900 years)

Releases radioactive particles and mercury into air

High CO2 emissions when burned

Severe threat to human health

High land use (including mining)

Severe land disturbance, air pollution, and water pollution

Very high environmental impact

Mining and combustiontechnology well-developed

Air pollution can be reduced with improvedtechnology (but addsto cost)

Advantages

Trade-Offs

Coal

Disadvantages

Fig. 13-15, p. 297

Tradeoffs of Coal

Low risk of accidents because of multiple safety systems (except in 35 poorly designed and run reactors in former Soviet Unionand Eastern Europe)

Moderate land use

Moderate land disruption and water pollution(without accidents)

Emits 1/6 as much CO2 as coal

Low environmentalimpact (without accidents)

Large fuel supply

Spreads knowledge andtechnology for building nuclear weapons

No widely acceptable solution for long-term storage of radioactive wastes and decommissioning worn-out plants

Catastrophic accidents can happen (Chernobyl)

High environmental impact (with major accidents)

Low net energy yield

High cost (even with large subsidies)

Subject to terrorist attacks

Advantages

Trade-Offs

Conventional Nuclear Fuel Cycle

Disadvantages

Fig. 13-19, p. 301

Tradeoffs of Nuclear Power

Chernobyl fallout – April 26, 1986

Improving Energy Efficiency

Big four energy-wasting devices

• Incandescent light bulb – wastes 95% of its energy input

• Nuclear power plants – 86% wasted • Internal combustion engine (e.g., car) – 75-80%

wasted

• Coal-burning power plants – 67% wasted

Saving Energy: Cars

Fuel-efficient cars account for <1% of all car sales in U.S.

• Relatively low cost of fuel

• Preference of SUVs and trucks

• Government’s failure to increase fuel economy standards

Fig. 13-24, p. 309

Hybrid Gas-Hybrid Gas-Electric CarElectric Car

Regulator Fuel Tank

Trans-mission

Battery bank

Combustionengine

Electric motor

Fuel

Electricity

Fuel-cell stackConverts hydrogenfuel into electricity

Front crush zoneAbsorbs crash energy

Electric wheel motorsProvide four-wheel driveHave built-in brakes

Hydrogenfuel tanks

Air systemmanagement

Body attachmentsMechanical locksthat secure thebody to the chassis

Universal docking connectionConnects the chassis with the Drive-by-wire system in the body

Rear crush zoneabsorbs crash energy

Drive-by-wiresystem controls

Side mounted radiatorsRelease heat generatedby the fuel cell, vehicleelectronics, and wheelmotors

Cabin heating unit

Fig. 13-25a, p. 310

Hydrogen Fuel-Cell CarHydrogen Fuel-Cell Car

© 2006 Brooks/Cole - Thomson

Fig. 13-25b, p. 310

Hydrogen Fuel-Cell CarHydrogen Fuel-Cell Car

What is E-85?What is E-85?

Flex-fuel vehicles can run on gas or any ethanol-gas mixture

Currently produced by Ford, Chrysler and GM

E-85• 85% ethanol / 15% gasoline• Florida only has 2 stations and neither are accessible to the public

Other Alternative Fuels

Biodiesel

P-series

http://www.eere.energy.gov/afdc/altfuel/altfuels.html• Compare different fuels• Find fueling stations• More information

Number of E85 stations

Any Questions?

News Story…Algal Fuel